Tetrachloroethylene, commonly known as perchloroethylene, is a synthetic halogenated hydrocarbon with excellent solvent properties. The primary physiological effect of tetrachloroethylene inhalation is central nervous system depression with loss of consciousness and death occurring at high concentrations. Liver damage has also been reported but only at or near lethal levels. The probability of environmental contamination is greatest at dry cleaning facilities where heated solvent vapors may be released to the atmosphere. Although adequate technology for the prevention of these losses is available, only 25% of the dry-cleaning establishments use such control. At metal degreasing facilities proper equipment design and adequate ventilation are sufficiently effective in maintaining safe vapor levels. The high volatility and low solubility of tetrachloroethylene are responsible for the entry of the solvent into the atmosphere and the primary mode of transport for tetrachloroethylene photodegrades in sunlight with a half life of 2 days and is therefore not expected to accumulate in the environment. Concentrations in the ambient air over the highly industrialized Los Angeles Basin averaged 1.25 ppb but levels over rural areas and the open ocean averaged only 20 ppt.